Door operators employ a mechanical device to replace the human effort of pushing or pulling a door. Automated doors make entrances accessible to disabled users as well as increase the convenience for all users.
A common door operator design uses a motor to open a door and a strong spring to close the door. As the door is opened, the spring is compressed. The relaxation of the spring returns the door to its original position. A significant limitation presented by these types of door operators is that they require a powerful motor to compress the spring.
An alternative door operator design eliminates the spring and uses a reversible motor to both open and close the door. Eliminating the spring greatly reduces the amount of power needed from the motor. Although a less powerful motor may be used, the motor must still be able to generate about 30 foot-pounds of force in order to move the door open and closed.
Small, low voltage electric motors offer many potential advantages in door operators. A small motor reduces the physical size of the door operator and allows for greater design flexibility. Low voltage motors are typically less expensive to maintain and operate than more powerful motors. Also, low voltage motors produce less noise than more powerful motors, which makes them well suited in locations such as hospitals, libraries, or houses of worship where quiet operation is preferred. Despite these advantages, low voltage electric motors have failed to gain widespread use in door operators. Low voltage electric motors generally operate at high speeds and produce low torque, making them unsuitable for use in automatic door operators.